In a mobile communication system or the like, a mobile terminal and a radio base station perform radio communication using a radio channel. As a multiple access scheme used in a mobile communication system, for a radio base station to perform radio communication with a plurality of mobile terminals at the same time, Frequency Division Multiple Access scheme (FDMA), Time Division Multiple Access scheme (TDMA), Code Division Multiple Access scheme (CDMA), etc. have been put to practical use.
In this mobile communication system, the moving speed of a mobile terminal may be estimated because it is used for, for example, position measurement of a mobile terminal, control of downlink transmission power of a radio base station, control of uplink transmission power of a mobile terminal, control of handover of a parameter in respective radio base stations at a time when a mobile terminal moves across cells, control of the average interval of a radio channel estimation result which is an estimation result of the state of a propagation path, or the like.
Conventionally, various means for estimating the moving speed of a mobile terminal in a radio base station have been proposed. Most of them obtain a moving speed based on an auto-correlation of a radio channel estimation result as described in, for example, Japanese Patent Laid-Open No. 2003-158779 (hereinafter referred to as Patent Document 1).
However, in the related mobile communication system as described above, there is a problem that estimation accuracy of a moving speed of a mobile terminal is degraded when there is a fixed frequency drift in the frequency of a radio channel used for radio communication between a radio base station and a mobile terminal.
In the mobile communication system, when there is a fixed frequency drift in a radio frequency used for radio communication between a radio base station and a mobile terminal, the mobile communication system operates to correct the frequency drift by a known AFC (Auto Frequency Control) technology in the radio base station. In a radio channel estimation result obtained in a state where the operation for correcting the frequency drift has not converged, an error component due to the frequency drift is contained.
In the related art described in above described Patent Document 1, since the moving speed of a mobile terminal is estimated using a radio channel estimation result containing an error component, estimation accuracy of the moving speed is degraded.